Device and method for detecting faults in a shielded instrument

ABSTRACT

A device and method for detecting faults in a shield of an electrosurgical instrument is described. The device has a relay configured to selectively interrupt power to the electrosurgical instrument, monitoring circuitry configured to monitor a shield in the electrosurgical instrument, control circuitry to control the relay, and a battery power source. The monitoring circuitry has an envelope detector and a detected average shield current detector. The monitoring circuitry is configured to compare a shield current peak value to a shield current peak threshold value, and to compare a detected average shield current value to a detected average shield current threshold value. The device is further configured to operatively couple an active electrode of an electrosurgical instrument and a return electrode to an electrosurgical generator.

CLAIM OF PRIORITY UNDER 35 U.S.C. § 119

The present Application for Patent is a continuation of U.S. patentapplication Ser. No. 14/302,281, filed Jun. 11, 2014, which is expresslyincorporated by reference herein as if presented in its entirety.

COPYRIGHT

A portion of the disclosure of this patent document contains materialthat is subject to copyright protection. The copyright owner has noobjection to the facsimile reproduction by anyone of the patentdisclosure, as it appears in the Patent and Trademark Office patentfiles or records, but otherwise reserves all rights available undercopyright law.

FIELD OF THE INVENTION

Aspects of the present invention relate to devices and methods fordetecting faults in electrosurgical instruments powered byelectrosurgical generators. In particular, but not by way of limitation,the present invention relates to systems and methods for detectingfaults in the insulation of a shielded electrosurgical instrument.

BACKGROUND OF THE INVENTION

Laparoscopic or electrosurgical instruments may have an insulated,conductive safety shield around an active electrode of theelectrosurgical instrument. During surgery, the physician can monitorcurrent passing through the shield to prevent the shield from causingunintended burns to the patient.

Various manners of monitoring the shield current are disclosed in U.S.Pat. No. 5,312,401 to Newton et al., U.S. Pat. No. 5,688,269 to Newtonet al., U.S. Pat. No. 8,007,494 to Taylor et al., and U.S. Pat. No.8,460,284 to Aronow, the disclosures of which are incorporated herein byreference in their entirety.

It should also be noted that, historically, the typical surgicalequipment, including power supplies, signal processing, computer, andoutput devices are connected to a mains or line ground which is the sameas the ground for the input power. Signals which come from points thatare not referenced to mains ground must be isolated using floating powersupplies and perhaps optical elements or transformers for the signalsthemselves. Further details of this construction are explained in U.S.Pat. No. 5,312,401 to Newton et al.

Although present devices are functional, their set-up and use requiresignificant oversight by operating room personnel, and they are bulkyand difficult to transport throughout the hospital. Accordingly, asystem and method are needed to address the shortfalls of presenttechnology and to provide other new and innovative features.

SUMMARY OF THE INVENTION

Exemplary embodiments of the present invention that are shown in thedrawings are summarized below. These and other embodiments are morefully described in the Detailed Description section. It is to beunderstood, however, that there is no intention to limit the inventionto the forms described in this Summary of the Invention or in theDetailed Description. One skilled in the art can recognize that thereare numerous modifications, equivalents and alternative constructionsthat fall within the spirit and scope of the invention as expressed inthe claims.

The present invention can provide a system and method for detectingfaults in the insulation of a shielded instrument. In one exemplaryembodiment, the present invention can include a device for detectinginsulation faults in a shielded electrosurgical instrument. The deviceincludes a relay configured to selectively interrupt power to theelectrosurgical instrument, monitoring circuitry configured to monitorelectrical signals associated with a shield in the electrosurgicalinstrument, and circuitry, responsive to the monitoring circuitry,configured to control the relay. The device also includes a batterypower source. The monitoring circuitry further comprises an envelopedetector and a wideband averaging detector and is configured to comparea shield current peak value to a shield current peak threshold value.The monitoring circuitry is also configured to compare a detectedaverage shield current value to a detected average shield currentthreshold value. The device is also configured to operatively couple anactive electrode of an electrosurgical instrument and a return electrodeto an electrosurgical generator.

A method for detecting faults within a shield of an electrosurgicalinstrument is also disclosed. The method comprises connecting a devicefor detecting insulation faults within a shield of an electrosurgicalinstrument, the device powered by an independent battery power source.The device is connected to an electrosurgical generator, theelectrosurgical generator configured to deliver power to anelectrosurgical instrument. The method also comprises monitoring set upsignals of the electrosurgical instrument, the set-up signals includinga connect sense and a battery power sense; monitoring electrical signalsassociated with a detected average shield current and a shield currentpeak; comparing the electrical signals with threshold electricalsignals; and controlling alarm indicators.

As previously stated, the above-described embodiments andimplementations are for illustration purposes only. Numerous otherembodiments, implementations, and details of the invention are easilyrecognized by those of skill in the art from the following descriptionsand claims.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present invention is apparent andmore readily appreciated by reference to the following DetailedDescription and to the appended claims, when taken in conjunction withthe accompanying Drawings, wherein:

FIG. 1 is an exemplary isometric view of a surgical environment.

FIG. 2 is a functional context diagram of an embodiment of the presentinvention.

FIG. 3 is a detailed functional context diagram of an embodiment of thepresent invention.

FIGS. 3A-3C are alternative functional context diagrams of theembodiment illustrated in FIG. 3.

FIG. 4 is a mixed circuit-block diagram of an embodiment the presentinvention.

FIG. 4A is a detailed mixed circuit-block diagram of the embodimentillustrated in FIG. 4.

FIGS. 5A-5C are circuit diagrams of embodiments of alternative faultdetectors of the present invention.

FIG. 6 is a section view of a cable according to one embodiment of thepresent invention.

FIG. 7 is a flow chart of one embodiment of a method according to anembodiment of the present invention.

DETAILED DESCRIPTION

Referring now to the drawings, where like or similar elements aredesignated with identical reference numerals throughout the severalviews, and referring in particular to FIG. 1, shown is an exemplarysurgical environment 1. For the purpose of this disclosure, it should beunderstood that the word “exemplary” is used herein to mean “serving asan example, instance, or illustration.” Any embodiment described hereinas “exemplary” is not necessarily to be construed as preferred oradvantageous over other embodiments. The surgical environment 1 includesa monitoring device 100, an electrosurgical generator 4, anelectrosurgical instrument 6, and a patient 8.

The device 100 is configured to be electrically coupled to theelectrosurgical instrument 6, the electrosurgical generator 4, and thepatient 8, to detect faults in the electrosurgical instrument 6. Thedevice 100 is operatively coupled to the electrosurgical instrument 6via an active electrode cable 112 and a shield current return cable 114,which may include two wires, one of which may be connected to circuitground. The active electrode cable 112 and the shield current returncable 114 may be enclosed by a common sheath (not shown) to simplifycable management.

The device 100 is further configured to couple the active electrodecable 112 to the electrosurgical generator 4 via an active cable link 3,which may be a short cable, as shown, or any other connecting mechanismsuitable for the high currents and voltages expected, including a manualswitching mechanism or integral pin and socket mechanism that wouldallow a simultaneous connection. More specifically, active cable link 3provides a means for operatively coupling the device 100 to any one of avariety of electrosurgical generators 4, which may not be standardizedacross the industry. Active cable link 3 may also require a secondcoupling step from the user, thus minimizing risk of unintendedcoupling.

Similarly, the device 100 operatively couples a return electrode cable120 to the electrosurgical generator 4 via return electrode connector 2coupled to a return electrode connector 10. In this embodiment, withinthe device 100, the shield current return cable 114 is operativelycoupled to the generator interface connector. It should be understoodthat, although shown as a generator interface connector and returnelectrode connector 10, the device 100 may operatively couple the returnelectrode cable 120 to the electrosurgical generator 4 in any mannersuitable to the expected working conditions. Further, one or more of theactive cable link 3, the return electrode cable 120, the activeelectrode cable 112, and the shield current return cable 114 may bepermanently pre-attached to the device 100. The return electrodeconnector 2 and active cable link 3 may comprise male plugs, and thereturn electrode connector 10 and active connector 5 may comprise femalereceptacles. However, it should be understood that any electricalcoupling system may be employed, including, but not limited to, maleplugs, female plugs, male jacks, female jacks or any other suitablemating system.

Turning now to FIG. 2, illustrated is an exemplary operational contextdiagram of the system 1 discussed above. At a high level, the device 100is configured to electrically couple an electrosurgical generator 4 toan electrosurgical instrument 6 by way of an active electrode cable 112,and a return electrode cable 120 to an electrosurgical generator. Thedevice 100 is configured to establish a closed circuit between theelectrosurgical generator 4, the electrosurgical instrument 6, and thepatient 8, as well as to provide a circuit ground, and a shield currentreturn mechanism. A contact quality monitored (CQM) return electrode 9may couple the return electrode cable 120 to the patient 8.

As discussed above, the active electrode cable 112 is configured todeliver a desired power to the electrosurgical instrument 6, while thereturn electrode cable 120 is configured to complete the circuit forsurgery. However, when faults are detected, it is necessary to interruptpower to the electrosurgical instrument 6, within about 0.6 seconds orless, to prevent thermal burns or overheating of tissue, and suchinterruption is achieved by way of a relay 102, as shown. The relay 102may be any relay 102 suitable for passing the high currents and voltagesexpected in the course of laparoscopic surgery or other surgicalinterventions. In some embodiments, the relay may be a vacuum reeddesign with a package that provides adequate clearance between the coiland contact, as well as sufficient internal insulation to withstand 5000V peak voltage. Provision for this clearance is present in the relayconnections and in other areas and this permits a peak voltage ratingfor the product of 4100 V including required safety margins. It shouldbe understood that the required safety margins, although generallyaround 20% in the industry, may change, thus necessitating a change inthe clearance.

During operation, normal currents flow through the shield 116 andthrough the device 100 to the return electrode cable 120 even when nofault exists. This is due to the high electrosurgical voltages appliedto the active electrode 7, as well as the inherent capacitance of theelectrosurgical instrument 6 and active electrode cable 112. Faultcurrents flow through the same path. However, fault currents aredistinguished from normal currents by two recognizable characteristicsof the faults. First, the fault currents tend to be larger than normalcurrents. The fault currents also tend to have a higher current peakvalue, due to inconsistent conduction through defects in the insulationof the shield 116. It is critical to detect fault currents quickly andreliably to prevent overheating of patient tissue.

As seen in FIG. 2, monitoring circuitry 106 is in electricalcommunication with control circuitry 108 and the instrument shield, andis configured to monitor electrical signals from the instrument shield116, which may include detectable physical quantities or impulses (suchas voltage, current, or magnetic field strength, by which messages orinformation can be transmitted. The control circuitry 108 is responsiveto signals from the monitoring circuitry 106 and is configured toinitiate a desired response in various hardware or active components ofthe device 100. That is, the control circuitry 108, upon receipt of afault signal from the monitoring circuitry 106, may open or close therelay 102 as necessary. In some embodiments, the control circuitry 108may cause audible, visual, or other warning signals 118 to be activatedin response to a signal from the monitoring circuitry 106 that a faultcondition exists.

As further seen in FIG. 2, the monitoring circuitry 106 and the controlcircuitry 108 may be integrated in a single unit; however, it should beunderstood that the monitoring circuitry 106 and the control circuitry108 may be separate and distinct units, or partially distinct units, aswill become apparent in the discussion below.

Turning now to FIG. 3, illustrated is a detailed operational contextdiagram of one embodiment of the system 1 described above. As seen, thedevice 100 may include a shield continuity circuit 124. The shieldcontinuity circuit 124 is configured to test electrical continuityacross the shield 116. If the shield 116 is malfunctioning, the shieldcontinuity circuit 124 is configured to open the relay 102, as well asto turn off a green LED 126. A logical inversion operation serves toturn a red LED 128 on. As should be apparent throughout this disclosure,the monitoring circuitry 106 and control circuitry 108 may compriseportions of the shield continuity circuit 124, the green LED 126 and thered LED 128 components.

Returning to FIG. 3, the device 100 may include as outputs one or moregreen LEDs 126 and red LEDs 128, and a relay 102 that may interruptpower delivered to the electrosurgical instrument 6. The relay 102 isclosed when the green LED 126 is illuminated during readyconditions—that is, the monitoring circuitry 106 does not detect a faultfrom the low battery detector 142, the envelope detector 130 or theshield current average detector 132, which will be discussed furtherbelow. Similarly, the relay 102 is open when the red LED 128 or otherwarning signal 118 is activated under fault conditions.

As discussed above, a current to voltage converter 122 may be providedfor converting a return shield current to a voltage signal. This voltagesignal is monitored by the envelope detector 130, which is configured todetect peak or peak-to-peak values, and a shield current averagedetector 132, which may be a wideband averaging detector, such as, butnot limited to, a full wave rectified average (FWRA), a half waverectified average, a mean squared, a root mean squared, or a mean powerdetector.

The envelope detector 130 is configured to compare the current peak to apreset threshold current peak value. If the current peak is greater thanthe preset threshold value, the relay 102 may be temporarily opened tointerrupt power to the instrument 6. Simultaneously, an audible warning134 may be activated. The interruption of power and the activation ofthe audible warning 134 may both be set to a limited timeframe. Forexample, the envelope detector 130 may include a 10 second timer 136 tolimit the interruption of power to the device to 10 seconds, and a 2second timer 138 may be included to limit the audible warning 134 to a 2second warning. The 10 second interruption is particularly effective inallowing the affected components of the electrosurgical instrument 6 tocool to a safe level when the device 100 quickly detects a fault andinterrupts power. Here, the device 100 may be configured to reliablydetect a fault and interrupt power to the electrosurgical instrument 6within about 10-130 milliseconds, before significant tissue damageoccurs, which is significantly faster than the 0.6 second time neededfor the instrument to heat to a temperature sufficient to cause tissuedamage, or about 44 degrees Celsius. Likewise, a 2 second timer 138 maybe sufficient to alert a surgical team of a fault without introducingunnecessary added distractions to the surgical team. It should beunderstood, however, that other timings may be desired or chosen. Insome situations, perhaps no or a longer, or shorter, or repeated audiblewarning is desired.

Continuing with FIG. 3, the device 100 also includes a shield currentaverage detector 132, which, in some embodiments, may be a widebandaveraging detector as previously discussed. The shield current averagedetector 132 is configured to compare the shield current detectedaverage to a preset threshold value. If the shield current detectedaverage is greater than the preset threshold value, the relay 102 may betemporarily opened to interrupt power to the electrosurgical instrument6, and an audible warning 134 may be activated, as discussed above. Itshould be understood that, although a FWRA method is exemplified in FIG.3, any averaging technique, such as a wideband average, may be used.

Also, as discussed above, a current to voltage converter 122 may beprovided for converting the shield current to a voltage signal. Thisvoltage signal is monitored by the envelope detector 130 and the shieldcurrent average detector 132. These circuits develop voltages which arecompared with thresholds to derive fault signals.

The device 100 may include monitoring circuitry 106 comprising an ORfunction 140. That is, if either the peak shield current or the shieldcurrent detected average exceeds a threshold value, power to theelectrosurgical instrument 6 may be interrupted. In some embodiments,the peak shield current or the shield current detected average mustexceed a threshold value for a predetermined period of time for a faultsituation to be indicated, so as to distinguish fault situations fromelectrical noise. In some embodiments, the device 100 may includemonitoring circuitry comprising a SUM function, wherein the sum of thepeak shield current and the shield current detected average must exceeda threshold value before a fault situation is indicated. In someembodiments, the sum must exceed a threshold value for a predeterminedlength of time for a fault situation to be indicated. In someembodiments, the device 100 may include monitoring circuitry comprisinga PROPORTIONAL function, wherein the ratio between the peak shieldcurrent and the shield current detected average must deviate from athreshold value before a fault situation is indicated. In someembodiments, the ratio between the peak shield current and the shieldcurrent detected average must deviate from a threshold value for apredetermined length of time for a fault situation to be indicated. Insome instances, the OR function, the SUM function, or the “PROPORTION”function may be configured to determine an approach to a secondthreshold value, the second threshold value being indicative of apotential, though not developed, fault.

The device 100 is powered by an independent battery power source 104 anddoes not require power from the electrosurgical generator 4, and a pinswitch 144 may be included in the device 100 to switch the battery powersource 104 to “on” when the device 100 is coupled to the returnelectrode connector 10. The battery power source 104 is referenced tocircuit ground via the shield conductor. To detect proper functioning ofthe battery power source 104, a low battery detector 142 is provided. Ifthe low battery detector 142 senses that the battery power source 104 isbelow a threshold charge, the green LED 126 is turned off, and the redLED 128 is activated.

In some embodiments, the device 100 is powered by a CR02 LithiumManganese cell, although any battery power source 104 suitable forproviding a nominal output, perhaps in the range of 2.9 volts, adequateto allow direct activation of the circuitry (including monitoringcircuitry 106 and control circuitry 108), LEDs 126, 128, audible warning134 and relay 102 is contemplated.

Turning now to FIGS. 3A-3C, alternate embodiments are now discussed. Forexample, in FIG. 3A, it is shown that, instead of an OR function, thedevice 100 may include a SUM function 148. That is, a fault is detectedwhere the sum of the peak value and the current detected average, whichmay be a wideband average, such as an FWRA calculation, exceeds athreshold value. The device 100 may be configured to require the sum toexceed a threshold value for a predetermined length of time beforedetecting a fault.

In FIG. 3B, it is shown that, instead of an FWRA, the device may includea different RF parameter detector 150 with an OR function 140. That is,a fault is detected where the peak value or the RF parameter exceeds athreshold value. The threshold value of the peak value and the thresholdvalue of the RF parameter are not necessarily the same. The device 100may be configured to require the peak value or the RF parameter toexceed a threshold value for a predetermined length of time beforedetecting a fault. The RF parameter detector 150 may be configured todetect one or more of: the detected average, real power in the shield150 a, the root mean square (RMS) of the real part of the shield current150 b, the RMS of the total current in the shield 150 c, the RMS of thetotal current in the shield below a certain active electrode voltage(referenced to the return electrode) 150 d, the magnitude of theimpedance or capacitance between the active electrode and the shield 150e, the resistance between the active electrode and the shield 150 f, andthe active electrode voltage (referenced to the return electrode) incombination with other signals 150 g. Some methods for detecting the RFsignals are described in U.S. Pat. No. 8,460,284.

In FIG. 3C, it is shown that a SUM function 148 may be used incombination with an envelope detector 130 and an RF parameter detector150 much like those discussed in relation to the embodiment shown inFIG. 3B. As previously mentioned, a PROPORTIONAL function may be usedinstead of the SUM or OR functions.

Turning now to FIGS. 4 and 4A, combined circuit and block diagrams ofembodiments of a portion of the monitoring circuitry 106 and controlcircuitry 108 are now discussed. As seen, the shield connection issensed at block 124, which may be a sensor in the monitoring circuitry106 previously described. In FIG. 4A, the shield current is sensed atR1, while C1 provides a low frequency isolation function and B1 is thebattery power source. The battery voltage is sensed and monitored, aswell as current passing through the insulation. The sensed variables arelogically monitored and combined to determine the ready (green LED) andfault (red LED) conditions. It should also be noted that the connectsense 124 and the control circuitry are both connected to the samecircuit ground, which reduces the overall size and electrical isolationelements required in the device 100.

Continuing with FIG. 4A, to indicate whether an instrument shield isconnected, a shield continuity circuit 124 includes a pair of shield Aand shield B wires, which are, in turn, coupled to the shield of anelectrosurgical instrument. If no insulation fault is detected, theshield is properly connected, and the battery is sufficiently charged,control circuitry, which may be a part of monitoring circuitry 106and/or control circuitry 108, is configured to allow the relay 102 toremain closed, and for the warning 118 to indicate ready conditions. Ifan insulation fault is detected, and the shield is not properlyconnected, or the battery is not sufficiently charged, the controlcircuitry is configured to open relay 102, and to cause the warning 118to indicate a fault or not-ready condition. Configuring the device 100,and hence the system 1, as shown in FIGS. 4 and 4A, that is, byconnecting the circuit ground to the shield, near the return electrodepotential, eliminates the necessity of large and expensive components toisolate the power supply and the fault current signal paths.

Continuing with FIG. 4A and FIG. 2, it should be noted that thegrounding scheme shown includes a grounding point that is common for allthe circuitry. The connect sense circuitry, current sensing resistor,detection circuitry, battery and control components are all connected toa common circuit ground point. This is close to the return electrodepotential but not exactly the same due to current flowing through thecurrent sense resistor R1 and the AC Coupling capacitor C1.

Sensing of an insulation fault condition is via processing of signalsprovided by a current sensing resistor and connected to rectification,filter, amplifier, and comparator circuits. That is, both a shieldcurrent average detector 132 and an envelope detector 130 are employed,with the envelope detector 130 comprising circuitry, or equivalents,thereof, as shown in FIG. 4.

As is further seen in FIGS. 4, R1 and R2 are configured to develop avoltage proportional to the current sensed. The voltage is directed totwo channels of current processing: the shield current average detector132, which may be a full-wave rectified average (FWRA) and the envelopedetector 130. C1, C2 connect the path to the shield current return andprovide a block for Faradic current that may develop, which wouldotherwise cause muscle stimulation in the patient under faultconditions.

D1, D2, C3 and C4 provide voltages that are proportional to the positiveand negative current averages. U8A sums these to output a voltageproportional to the shield current detected average value for the highfrequency current waveform. This is compared to a fixed threshold valueand if above the threshold, triggers an alert.

Continuing with FIG. 4, it is shown that D6, D7, C20 and C23, withadditional filtering, provide voltages that are proportional to thepositive and negative current peaks. These are summed by U8D so that theoutput voltage is proportional to the shield current peak to peak value.This is compared to a fixed reference, and if the value is greater thanthe threshold value, the control is configured to trigger an alert andinterruption of power. For both current channels from the shield currentaverage detector 132 and the envelope detector 130, once an alert istriggered, the 10 second timer opens the relay via U2 and causes acessation of electrosurgical power for that interval and illuminates thered LED.

Turning now to FIGS. 5A-5C, other embodiments of a portion of themonitoring circuitry 106 are shown. As seen in FIG. 5A, a SUM functionmay be incorporated, such that the average shield current, which may bea wideband average current, is summed with the current peak. If the sumis greater than a present threshold value, a fault condition isindicated. For example, analog outputs of the current average and peakchannels are summed prior to the comparator function, and this may beachieved by way of a resistor network. In this case, a fault signal isgenerated when the sum of the peak and shield current average channelsis above a preset threshold value. One advantage to this arrangement isthat, when the total signal begins to approach the preset thresholdvalue, the system is inherently more sensitive to small increases in thepeak channel response, which reduces the likelihood of a false negativeresponse to a spark through insulation.

In FIGS. 5B and 5C, it is shown that a PROPORTIONAL function may be usedinstead. Here, a comparator for the peak sensing channel is suppliedwith a variable threshold value, rather than a fixed threshold value. Itshould be understood that, to prevent an indeterminate output stateunder low signal conditions, a fixed base is supplied, so that thecomparator always has a non-zero reference input. The variable thresholdvalue may be accomplished using a resistor network connected to theoutput of the shield current average channel. In the PROPORTIONALfunction, a fault signal is generated when the output of the peakchannel is greater than the variable threshold value. One advantage ofusing the PROPORTIONAL function is that more sensitive detection of aninsulation sparking condition is made possible at low current operatinglevel, as compared to the circuitry having the OR function of FIG. 3.

In some embodiments, the OR function may be combined with a SUM functionand/or a PROPORTIONAL function, so as to provide desired increasedsensitivity at lower operating levels as approaching preset thresholdvalues.

Turning now to FIG. 6, a cable 600 for use with device 100 is nowdiscussed. As previously mentioned, various cables or wires can besheathed together to improve cable management, and here, cable 600comprises shield wire 601, shield wire 602, and active wire 603. Each ofthe wires 601, 602, 603 is individually sheathed, and all are sheathedtogether in outer sheath 606. Further, string fillers 604 and pvc filler605 and/or other low dielectric constant materials are provided toensure adequate spacing between the wires 601, 602, 603 whilemaintaining low capacitance and adequate flexibility of the cable 600.The arrangement of cable 600 as shown in FIG. 6 enables high voltages tobe carried through the active wire 603 without modification for use in amonopolar device; that is, prior art techniques requiring substantiallyreducing the voltage experienced by the active wire 603 are not requiredin cable 600, and thus in device 100.

Turning now to FIG. 7, some embodiments of a method 700 are nowdescribed. The method comprises coupling a device 702 for detectingfaults, monitoring setup signals 704, monitoring shield signals 706,generating dependent variables 708, comparing signals and dependentvariables to threshold value(s) 710, and controlling alarm indicators712.

Coupling the device 702 comprises coupling the device to anelectrosurgical generator 4 and an electrosurgical instrument 6 that hasa shield 116. One or both of the electrosurgical generator 4 and theelectrosurgical instrument 6 may be similar to the electrosurgicalgenerator 4 and electrosurgical instrument 6 discussed above withreference to FIGS. 1-5. It should be understood that the device 100 maybe coupled to the electrosurgical instrument 6 before or after thedevice 100 is coupled to the electrosurgical generator 4. In someembodiments, coupling the device 702 to the electrosurgical generator 4may be achieved by coupling a return electrode connector 2 to a returnelectrode connector 10 of the electrosurgical generator 4. The returnelectrode connector 2 may be configured to operatively couple both ashield current a return electrode current to the return electrodeconnector 10 by way of the device 100. The return electrode connector 10may further be configured to receive a pin to actuate a pin switch 144.Coupling the device 702 to the electrosurgical generator 4 may furthercomprise connecting a pre-attached active cable link 3 to an activeconnector 5 of the electrosurgical generator 4. Coupling the device 702to the electrosurgical instrument may be include connecting an activeelectrode cable 112 to the electrosurgical instrument 6. The activeelectrode cable 112 may be pre-attached to the device 100.

Monitoring setup signals 704 comprises monitoring a shield circuit todetect connection of a shield, as well as monitoring for low batterypower of the device itself.

Monitoring shield current values 706 comprises monitoring electricalquantities associated with the shield current. The electrical quantitiesof the shield current may include the current peak value and thedetected average current value captured and calculated respectively at agiven time. The detected average current value may be a widebandaverage, such as, but not limited to, an FWRA value, or an RMS value,for example. The electrical quantities associated with the shieldcurrent may include the detected average, real power in the shield, theroot mean square of the real part of the shield current, the RMS of thetotal current in the shield, the RMS of the total current in the shieldbelow a certain active electrode voltage (referenced to the returnelectrode), the magnitude of the impedance or capacitance between theactive electrode and the shield, the resistance between the activeelectrode and the shield, and the active electrode voltage (referencedto the return electrode) in combination with other quantities. A morecomplete understanding of monitoring shield signals 706 may be had byreferencing the previous FIGS. 1-5C and the preceding discussion ofdevice 100.

In some embodiments, monitoring shield signals 706 may comprisegenerating dependent variables based on the signals monitored. Thedependent variables may be, for example, a SUM of the detected averagecurrent and the current peak, or a PROPORTION of the detected averagecurrent to the current peak

Comparing 708 to threshold values may comprise comparing the shieldcurrent peak value to a shield current peak threshold value andcomparing the detected average shield current value to a detectedaverage shield current threshold value. Sensing a fault condition mayfurther initiate an audible warning 134 and or a visual warning, such asa red LED 128.

In some embodiments, comparing 708 to threshold values may comprisecomparing a dependent variable to a threshold dependent variable value,such as a SUM value or a PROPORTION value to a threshold sum value or athreshold proportion value.

Comparing 708 to threshold values may also include comparing a portionof the voltage of the independent battery power source 104 to a devicevoltage reference, which, in some embodiments, may be 1.24V.

The method 700 further includes controlling 710 alarm indicators and arelay. Controlling 710 comprises indicating ready conditions and closinga relay when the device is in a ready condition, as discussed previouslyin this document. Controlling 710 may comprise indicating faultconditions and opening a relay if a fault is detected. Controlling 710may include alerting a user when the voltage of the battery power source104 drops to a predetermined threshold voltage. The predeterminedthreshold voltage should be greater than the voltage specification ofthe monitoring circuitry 106 and control circuitry 108 of the device100. In some embodiments, the threshold voltage may be about 2.6V.

The method 700 may include applying power to the electrosurgicalinstrument 6, determining that the shield current peak value is greaterthan the shield current peak threshold value, and interrupting power tothe electrosurgical instrument 6. The method 700 may include determiningthat the detected average shield current value is greater than thedetected average shield current threshold value, and interrupting powerto the electrosurgical instrument 6. Power may be interruptedtemporarily, for example, for a predetermined period of time, or powermay be permanently interrupted, for example, where a permanent failureis detected. It should be understood that power interruption may be anOR function, wherein power is interrupted if any one of the shieldcurrent peak value, the detected average shield current value, shieldconnect sense, and battery voltage are outside a desired range. That is,any of the above values may indicate a fault condition. In someembodiments, a fault condition may be required to exist for apredetermined length of time greater than zero.

In an alternative embodiment, the method 700 may include applying powerto the electrosurgical instrument 6, determining that a summation of theshield current peak value and the detected average shield current valueis greater than a summation threshold value, and interrupting power tothe electrosurgical instrument 6. Here, it should be understood thatpower interruption may be an OR function, wherein power is interruptedif the current summation value or the battery voltage are outside adesired range. That is, either of the above two values may indicate afault condition. In some embodiments, a fault condition may be requiredto exist for a predetermined length of time greater than zero.

The method 700 may include applying power to the electrosurgicalinstrument 6, determining that a fault condition in the shield 116exists, and interrupting power to the electrosurgical instrument 6 for apredetermined length of time. The predetermined length of time may bearound 10 seconds, or any other length of time suitable for ensuringexcess heat is dissipated from the fault site.

In conclusion, the present invention provides, among other things, adevice, system and method for detecting faults in an electrosurgicalinstrument shield. Those skilled in the art can readily recognize thatnumerous variations and substitutions may be made in the invention, itsuse and its configuration to achieve substantially the same results asachieved by the embodiments described herein. Accordingly, there is nointention to limit the invention to the disclosed exemplary forms. Manyvariations, modifications and alternative constructions fall within thescope and spirit of the disclosed invention as expressed in the claims.

What is claimed is:
 1. A device for detecting insulation faults in ashielded electrosurgical instrument, comprising: a relay configured tointerrupt power to the electrosurgical instrument; monitoring circuitryconfigured to monitor electrical signals associated with a shield in theelectrosurgical instrument; control circuitry configured to control therelay; and a battery; wherein the device is configured to operativelycouple an active electrode of the electrosurgical instrument and areturn electrode to an electrosurgical generator; wherein the monitoringcircuitry comprises, a current to voltage converter configured toconvert a return current of the shield into a voltage signal of theshield; an envelope detector configured to detect a peak value of thevoltage signal of the shield; a full wave rectified average detectorgenerating a full wave rectified average value of the voltage signal ofthe shield; a low fault threshold detector configured to generate a lowfault threshold based on a current value in the shield of theelectrosurgical instrument; and an output comparator coupled to themonitoring circuitry and configured to generate a fault condition whenthe peak value of the voltage signal of the shield is greater than thelow fault threshold.
 2. The device of claim 1, wherein the controlcircuitry comprises a warning device responsive to the monitoringcircuitry.
 3. The device of claim 1, wherein the control circuitry isconfigured to interrupt power to the electrosurgical instrument when atleast one of: the peak value of the voltage signal of the shield isgreater than a shield current peak threshold value; and the full waverectified average value of the shield is greater than an average shieldcurrent threshold value.
 4. The device of claim 1, wherein themonitoring circuitry, the control circuitry, and the battery areconnected to a common circuit ground point.
 5. The device of claim 1,wherein the device is configured to operatively couple the returnelectrode to the electrosurgical generator.
 6. The device of claim 1,wherein the device further comprises a shield current return connectorconfigured to operatively couple the return current of the shield to theelectrosurgical generator.
 7. A system for detecting insulation faultswithin a shielded electrosurgical instrument, comprising: anelectrosurgical generator; an electrosurgical instrument having a shieldelectrically coupled to the electrosurgical generator; a battery;monitoring circuitry configured to monitor electrical signals associatedwith the shield in the electrosurgical instrument; control circuitryresponsive to the monitoring circuitry, configured to control a relay;wherein the monitoring circuitry comprises a current to voltageconverter configured to convert a return current of the shield into avoltage signal of the shield; an envelope detector configured to detecta peak-to-peak value of the voltage signal of the shield; a full waverectified average detector generating a full wave rectified averagevalue of the voltage signal of the shield; and where the monitoringcircuitry is configured to at least perform one of: (a) interruptingpower to the electrosurgical instrument when the peak-to-peak value ofthe voltage signal of the shield exceeds a shield current peak to peakthreshold value; (b) interrupting power to the electrosurgicalinstrument when a summation of the peak-to-peak value and the full waverectified average value is greater than an active voltage thresholdvalue; or (c) interrupting power to the electrosurgical instrument whenthe full wave rectified average value is greater than a variable shieldcurrent peak to peak threshold value.
 8. The system of claim 7, whereinthe monitoring circuitry is configured to interrupt power to theelectrosurgical instrument for a predetermined period of time.
 9. Amethod for detecting insulation faults in a shielded electrosurgicalinstrument, comprising: connecting a device for detecting instrumentinsulation faults to an electrosurgical generator, the device powered bya battery power source, the electrosurgical generator configured todeliver power to an electrosurgical instrument; coupling the device to ashielded electrosurgical instrument; monitoring set up signals of theshielded electrosurgical instrument, the set up signals including aconnect sense and a battery power sense; monitoring a return current ofthe shielded electrosurgical instrument; determining a peak value of thevoltage signal of the shield; determining a full wave rectified averagevalue of the voltage signal of the shield; interrupting power to theelectrosurgical instrument when at least one of the conditions are met:a) the peak value exceeds a shield current peak threshold or the fullwave rectified average value exceeds the full wave rectified averagethreshold value; b) a summation of the peak value and the full waverectified average value exceeds a summation shield threshold value; orc) the full wave rectified average value is greater than a variablepeak-to-peak threshold value; and controlling alarm indicators.
 10. Themethod of claim 9, comprising: interrupting power to the electrosurgicalgenerator when the peak value exceeds the shield current peak thresholdand the full wave rectified average value exceeds the full waverectified average threshold value.